The present invention relates to a projector apparatus comprising light valves.
In recent years, there are becoming widespread projection type projector apparatuses, each of which uses three TFT (Thin Film Transistor) liquid crystal display panels corresponding to the three primary colors of RGB (red, green and blue), (hereinafter referred to as a 3-plate projector apparatus). This projector apparatus projects images on a large screen hung on the wall or a semi-transparent screen such as a Fresnel lens to provide realistic images on the large screen appealing strongly to the watchers. This projector apparatus comprises an optical system and a driving control system of the optical system that are all housed in the apparatus. The light emitted from a light source of the optical system is splitted into RGB colors, then modulated by light valves, each of which comprises a liquid crystal panel, according to the drive signals generated by the driving control system, then combined again to form color images.
FIG. 1 is a schematic diagram illustrating an example of the optical system of such a projector apparatus.
The light W emitted from the light source 31 is incident on the dichroic mirror 32 to be splitted into red light R, green/blue light G/B, for which the light R is reflected and the light G/B is transmitted.
The light R splitted by reflecting on the dichroic mirror 32 is further reflected by the mirror 33, then modulated by the light valve LB11 that controls transmission of the red light and led to the dichroic mirror 34. The light G/B transmitted through the dichroic mirror 32 reaches the dichroic mirror 35, and is splitted into lights G and B. The light G splitted by reflecting on the dichroic mirror 35 is modulated in the light valve LB12 that controls transmission of green light, then led to the dichroic mirror 34 and reflected therefrom so as to be combined with the light R and led to the dichroic mirror 37 as a light R/G. In the meantime, the light B transmitted through the dichroic mirror 35 is modulated by the light valve LB13 that controls transmission of blue light, then reflected by the mirror 36 and led to the dichroic mirror 37.
The dichroic mirror 37 transmits the light R/B led from the dichroic mirror 34 and reflects the light B reflected from the mirror 36, so that the lights with those 3 colors are combined. The combined light RGB is enlarged through a projection lens 38 and projected on, for example, a screen hung on the wall.
The light source 31 used for the projector apparatus shown in FIG. 1 has emission characteristics with various spectral distributions depending on the lamp in use. Therefore, when selecting three chromaticity points meeting the EBU (Europe Broadcast Union) Standard for each of RGB for a light source having a spectral distribution, for example, as shown in FIG. 2, it becomes difficult to reproduce the color correctly because the green color purity is changed by the color (orange) represented by the spectrum peak generated around the wavelength of 590 nm.
To avoid this, there is an idea to cut this orange light to improve the color purity. In this case, however, the efficiency to use the light from the light source is lowered, causing the dynamic range to be narrowed to make the degree of whiteness become insufficient.
Conventionally, when priority is given to the color purity over others, the efficiency to use light is lowered. On the contrary, when the efficiency to use light is improved with the strong light generated around the wavelength of the green light being included in the green region or red region, the color purity must be sacrificed to some extent depending on the emission characteristics of the lamp used as the light source.
In order to solve such problems, the present invention provides a projector apparatus comprising a light source, an optical system comprising a dichroic mirror as a light-splitting device for splitting for the light emitted from the light source into lights with specified colors and light valves for carrying out optical modulation of the splitted lights; and a driving processing system for generating color drive signals for driving the light valves according to color image signals, wherein the driving processing system includes a drive signal generator for generating at least four channels of the color drive signals from color image signals of the three primary colors, each of the color drive signals corresponding to at least four kinds of colors including colors selected according to the spectrum of the light source, and the optical system includes the light-splitting device for splitting the light from the light source into at least four lights according to the colors corresponding to the color drive signals generated by the drive signal generator; light valves for carrying out optical modulation of the splitted lights, for which the light from the light source is splitted by the light-splitting device, according to the color drive signals; and a combining device for combining the lights modulated by the light valves.
According to the present invention, at least four color drive signals corresponding to the required chromatic points according to the light source spectral distribution are generated from inputted image signals, and four light valves to be driven by the color drive signals are provided. Thus, the fourth light valve is driven by the fourth color drive signal in addition to the three light valves driven by three kinds of color drive signals corresponding to the three primary colors of RGB, so that the efficiency to use the light source can be improved and the color reproduction range can be expanded significantly. Consequently, even when monitoring images of an ordinary image source, the image can be represented at points where both saturation and luminance on the luminance axis are higher than those of the projector apparatus of the related art.
Furthermore, more improved representation of luminance becomes possible with the constraint condition in generating four or more kinds of color drive signals, so that gradation can be much improved. Furthermore, image resolution can be improved by splitting luminance component effective for improving resolution and by providing four or more light valves. Furthermore, the present invention allows a portion where the efficiency to use the light is improved can be represented by at least 4 values, the peak luminance can be improved, as well as this peak luminance can be used to enable modulation.